Polycarbonamides having an improved antistatic property



3,388,104 Patented June 11, 1968 ICC 3,388,104 POLYCARBONAMIDES HAVINGAN IMPROVED ANTISTATIC PROPERTY Lawrence W. Crovatt, Jr., Raleigh, N.C.,assignor to Monsanto Company, St. Louis, Mo., a corporation of DelawareNo Drawing. Continuation-impart of application Ser. No. 579,509, Sept.15, 1966. This application Oct. 11, 1967, Ser. No. 674,662

7 Claims. (Cl. 260-78) ABSTRACT OF THE DISCLOSURE Polyamides, useful inthe production of fibers which have greatly improved anti-staticproperties, are produced by incorporating into the polymer prior tofilament formation from 0.1 to 20.0 weight percent of a polyalkyoxylatedtriglyceride of a saturated fatty acid having 10 to 30 carbon atoms.

This application is a continuation-in-part of SN. 579,- 509 filed Sept.15, 1966, now abandoned which in turn is a continuation-in-part of SN.422,822 filed Dec. 31, 1964, now abandoned.

The polymeric substances of which this invention is concerned aresynthetic high molecular weight fiber-forming polycarbonamides of thegeneral type characterized by the presence of recurring carbonamidegroups as an integral part of the polymer chain, and wherein such groupsare separated by at least two carbon atoms. They are furthercharacterized by high melting point, pronounced crystallinity andinsolubility in most solvents except mineral acids, formic acid andphenols. Upon hydrolysis with strong mineral acids the polymers revertto the reactants from which they were formed.

The polyamides of this type are usually made by heating either (a)substantially equirnolecular proportions of a diamine and dicarboxylicacid or (b) various amino acids and amide-forming derivatives thereofuntil the material has polymerized to the fiber-forming stage, whichstage is not generally reached, until the polyamide has an intrinsicviscosity of at least 0.4, the intrinsic viscosity being defined as:

Hm e 1:) O O C in which 1;, is the relative viscosity of a dilutesolution of the polymer in m-cresol in the same units and at the sametemperature and C is the concentration in grams of polyrner per 100 cc.of solution. The polymers thus obtained have high melting points and canbe cold drawn to form strong highly oriented fibers.

The diamines and dicarboxylic acids and amide-forming derivativesthereof which can be used as reactants to yield the fiber-formingpolyamides are well known in the art. Suitable diamines may berepresented by the general formula in which n is an integer of two orgreater, preferably from 2 to 10. Representative examples are ethylenediamine, propylene diamine, tetramethylene diamine, pentylmethylenediamine, hexamethylene diamine, octamethylene diamine, and decamethylenediamine. Suitable dicarboxylic acid reactants are represented by thegeneral formula:

HOOCRCOOH in which R is a divalent hydrocarbon radical having a chainlength of at least two carbon atoms. These dicarboxylic acids may beillustrated by sebacic acid octadecanedioic acid, adipic acid, subericacid, azelaic acid, un-

decanedioic acid, glutaric acid, pimelic acid, brassylic acid, andtetradecanedioic acid.

In place of the above-noted dicarboxylic acids and diamines theamide-forming derivatives thereof can be employed to form fiber-formingpolymers. Amide-forming derivatives of the diamines include thecarbamates and N-formyl derivative. Amide-forming derivatives of thedibasic carboxylic acids comprise the monoand di-ester, the anhydride,the monoand diamide, and the acid halide.

In addition to the above diamines and dicarboxylic acids and theirderivatives, the polyamides of this invention may be prepared fromcertain of the amino acids. The amino acids are represented by thegeneral formula:

H N(CH COOH in which n is an integer of four or more and preferably from4 to 11. Illustrative examples of these amino acids are 6-aminocaproicacid, 7-amino-heptanoic acid, 8- aminooctanoic acid, 9-aminononanoicacid, IO-aminodecanoic acid, ll-aminoundecanoic acid, l2-aminododecanoicacid, 13-arninotridecanoic acid, and 22-aminobehenic acid. Also thelactams of these amide acids may be used as monomers from which thepolyamides of the present invention may be prepared.

In addition to the homopolyamides, copolyamides and terpolyamides arealso contemplated and are within the scope of this invention. Thecopolyamides and terpolyamides are obtained in known manner. That is,mixtures of diamines and dibasic acids, are used in forming the coandter-polymers, with the diamine being present in substantially equimolarproportions to the total dibasic acids present during thepolymer-forming reaction. The 00- and ter-polymeric products may beformed directly from the corresponding monomers, or one or morehomo-polymers may be added to the polymerizable reactants, distributionof the desired units entering the products via amide interchange.Formation of the desired diamine salts of the various dibasic acidsprior to melt polymerization assist in control of the reaction. Theconventional polyamide melt polymerization cycle is suitable.

It is known that fibers obtained from the polyamides prepared from someof the above reactants have obtained wide commercial importance andsuccess. Although the fibers prepared from these polyamides have much tocommend them, there is still need for new and improved properties. It iscommon knowledge that fibers prepared from these conventional polyamidestend to collect and retain, for periods of time, static electricalcharges when coming into contact with each other or into contact withforeign objects. This problem is particularly severe under conditions oflow humidity, which is often the case during winter months. Theelectrostatic charge build-up on the fibers can occur quite rapidly andoften times dissipation of the charge into the environmental atmosphereis extremely slow; a consequence of which, is that the polyamide articlemay remain electrostatically charged for hours at the time. Thisproperty tends to make the filaments difiicult to handle duringmanufacturing operations and results in objectionable fiber properties,particularly in wearing apparel. Electrostatically charged textilematerials may not only repel each other but may also attract and holdsuch things as dust, dirt and lint. The accumulation of static chargesand the slow dissipation thereof on the fibers prevents finished,synthetic fabrics from draping and wearing in a desirable manner, andcauses the same to cling uncomfortably to the body of the person wearingthem. Fibers having a high electrostatic susceptibiilty often cling toguides and rolls in textile machinery during the manufacturing andprocessing thereof and are sometimes seriously damaged and weakened. Asa result, the quality of the end product is lower than it mightotherwise be.

For these reasons, and because end-uses such as garments, upholstery,hosiery, rugs, blankets and fabrics are greatly benefited by a reducedtendency to accumulate and maintain electrostatic charges, a permanentanti-static property as a characteristic of the polymer and the fibersproduced therefrom is highly desirable.

Presently, in the commercial production of nylon fibers the as-spunfilaments are given a treatment to improve their electrostatic andhandling properties. This treatment usually consists of passing thefilaments, while in the form of a bundle, through a bath or over a wheelcoated with a treating or finishing liquid. The finish thus received bythe filaments is nothing more than a coating and is not of a permanentnature. Most, if not all of the anti-static agent on the fiber surfaceis lost in subsequent processing of the filament by mechanical handling,heating, washing, scouring and dyeing. If the anti-static agent doesremain on the fiber until the final end product is produced it oftenbecomes less effective after the end product is used for a period oftime, and especially after a number of washings or dry cleaningoperations.

Efforts have been made in the past to produce permanent antistaticpolyamide fibers and articles by the application of a more permanentcoating. Also, efforts utilizing hydrophilic anti-static type comonomersin the polyamide formation have been tried. For various reasons such asa resulting harsh fiber surface or sacrifice to good fiber physicalproperties, these methods have not been satisfactory.

Accordingly, it is an object of the present invention to providemodified polyamides and fibers produced therefrom which possess a highrate of dissipation of electrostatic charges.

Another object of this invention is toprovide modified polyamides andfibers produced therefrom which possess a high resistance to theaccumulation of electrostatic charges.

It is still a further object of this invention to provide modifiedpolyamides and fibers derived therefrom which possess a permanentantistatic property even after multiple washings.

These and other objects and advantages will become apparent in thecourse of the following detailed description of the invention.

In general, these objects are attained by providing a fiber-formingsynthetic linear polycarbonamide having recurring amide groups as onintegral part of the main polymer chain, and wherein said groups areseparated by at eleast two carbon atoms, containing from 0.1 to about20.0 weight percent, based on the weight of said polycarbonamide, of apolyalkyoxylated triglyceride of a saturated fatty acid having 12 to 30carbon atoms. These triglycerides may be represented by the formula:

wherein a and b are integers from 2 to 26 with the proviso that the sumof a+b is at least 10. E is an alkyleneoxy radical containing 2 to 5carbon atoms, and x, y, and z are integers greater than zero and whereinthe sum of x+y+z is equal to a value of between 50 and 500.

The polyoxyalkylene portion of the glyceride i.e., (E) (E) and (E)should be in the molecular weight range between 2,000 and 22,000 and maybe ethoxy, propoxy, butoxy, or pentoxy. The long chain saturated fattyacids of the triglyceride may have from 12 to about 30 carbon atoms,with 12 to 25 being preferred. A preferable concentration of themodifying agent to be used is from 1.0 to 15.0 weight percent. Thesepolyalkoxylated triglycerides are particularly desirable modifyingagents as they are very stable in the melt polymerization cycle, theprocessing procedures and under the conditions of use.

The polyalkoxylated triglyceride may be added to the polymer-formingreactants at the initial stage of the polymerization or during thecourse of the polymerization. This modifying agent may also be dispersedinto the polymer melt just prior to extrusion into filaments or it maybe mixed with polymer flake prior to the melt spinning of the flake.

The long chain saturated fatty acids, which make p the triglyceride, maycontain from 12 up to about 30 carbon atoms with 12 to 25 beingpreferred. Examples of suitable acids which are within the scope of anduseful in this invention are the hydroxy derivatives of lauric acid,myristic acid, palmitic acid, stearic acid, behenic acid, cerotic acid,and the like. The hydroxy derivatives of these saturated fatty acids areeasily produced by hydroxylating the corresponding unsaturated fattyacid by known methods. If necessary after hydroxylation, any

remaining double bonds may be removed by hydrogenation, for example withhydrogen gas. It is important, however, that the triglyceride used inthe present invention be free from carbon to carbon unsaturation. Thereason for this is that the unsaturated fatty acid portion is subjectedto degradation under the conditions to which polyamide fibers arenormally subjected, which degradation results in yellowing of thefilaments.

A preferred modifying agent in accordance with this invention is theethoxylated triglyceride of hydroxy stearic acid. One reason for thepreference of this compound is that it is readily available as aderivative of castor oil. Castor oil is known to consist of about 88percent of the glyceride ester of ricinoleic acid, which may berepresented by the following formula:

when the above glyceryl triricinoleate is polyethoxylated by knownmethods, it yields a compound of the following structure:

wherein x, y, and z are integers as defined above. When the glyceryltriricinoleate is hydrogenated prior to polyethoxylation then theproduct of the polyethoxylation may be designated polyethoxylatedhydrogenated castor oil,

or polyethoxylated glyceryl tristearate and would have the structure:

H2COC\CHz-/ICHC H1 This compound is preferred due to its availabilityand to its ability to be purified to a high degree and thus thediscoloration of the polycarbonamide to which it is added is extremelyslight.

The amount of alkylene oxide attached to the triglyceride is importantto the extent that it must be sufficient to allow for good dispersion inthe polymer. It has been found that less than about 50 moles (i.e.,about 2,000 M.W.) results in a poorly dispersed modifying agent. About500 moles (i.e., about 22,000 M.W.) has been found to be the practicalupper limit since it is very difficult to alkoxylate the triglyceridewith higher molecular weight material.

The modified synthetic linear polyamides as described herein areprepared by procedures well known in the art and commonly employed inthe manufacture of unmodified polyamides. That is, the reactants areheated at a temperature of from 180 C. to 300 C., and preferably from200 C. to 295 C. until the product has sufficiently high molecularweight to exhibit fiber-forming properties. This condition is reachedwhen the polyamide has an intrinsic viscosity of at least 0.4 inaccordance with the definition of intrinsic viscosity as given hereinabove. The reaction can be conducted at superatmospheric, atmospheric orsubatmospheric pressure. Often it is desirable, especially in the laststage of the reaction, to employ conditions, e.g., reduced pressure,which will aid in the removal of the reaction by-product. Preferably,the reaction is carried out in the absence of oxygen e.g., in anatmosphere of nitrogen.

For convenience, when a diamine and dicarboxylic acid are used in thepreparation of a polyamide, it is usually desirable that thedicarboxylic acid be introduced into the reaction as a preformed salt,i.e., diamine salt. However, this is a matter of convenience only sincethe dicarboxylic acid and a corresponding molecular quantity of diaminemay be in the form of uncombined diaciddiamine when brought into thereaction zone.

The synthetic linear polycarbonamides of this invention may be prepared,spun and drawn under conventional, polyamide-forming productionconditions. In addition to the aforedescribed modifying agents,delustrants, antioxidants, plasticizers, viscosity stabilizers, andother like materials may be used in the preparation of the polyamides ofthis invention.

The novel polycarbonamides of the present invention are of primaryinterest for use in the manufacture of filaments, yarns and fabrics.They are, however, equally useful in end products such as films,coatings, bristles, fillings, flock, cables and the like.

In order to illustrate the invention and the advantages thereof withgreater particularity, the following specific examples are given. Itshould be understood that they are intended to be only illustrative andare not intended to limit the invention and claims thereof. Parts andpercentages are by weight unless otherwise indicated.

Example I This example illustrates the preparation of a conventionalfiber-forming polyamide and is to be used as a standard of comparisonwith polyamides of the same type modified in accordance with thisinvention.

A solution parts of hexamethylene diammonium adipate (nylon 66 salt)dissolved in 50 parts of water was added to stainless-steel highpressure autoclave. The autoclave was equipped with a stirrer allowingthe contents thereof to be agitated. The unit was purged of oxygen bythe use of purified nitrogen. Next, the temperature and pressure wereslowly raised until values of 243 C. and 250 p.s.i.g., respectively,were reached, during which time there was a continuous removal of steamas condensate. Also, during this period of temperature and pressureincrease the mixture was continuously agitated. At this point thepressure reduction cycle began. The pressure was gradually reduced toatmospheric over a 25 minute period and the polymer melt was allowed toequilibrate for a period of 30 minutes at 278 C.

Upon completion of polymerization, the finished polymer was melt spundirectly from the bottom of the autoclave through a l4-hole spinneret toyield a white multi-filament yarn. This yarn when drawn at a draw ratioof 4.7:1 possessed a tenacity of 6.12 grams per denier. The yarn waslater converted to a fabric suitable for static testing.

Example II This example illustrates the preparation of filaments fromthe polymer, polyhexamethylene adipamide modified in accordance withthis invention.

The following materials were added to a stainless-steel high-pressureautoclave; 150 parts of hexamethylene diammonium adipate, 50 parts ofwater, and 2.0 weight percent (based on the weight of the unmodifiedpolyamide) of hydrogenated castor oil polyethoxylated with 200 moles ofethylene oxide per mole of the glyceride. The autoclave was then purgedof air using purified nitrogen. Next, the temperature and pressure inthe autoclave were slowly raised until values of 220 C. and 250p.s.i.g., respectively, were reached. The temperature was then furtherincreased to 243 C. while the pressure was maintained at 250 p.s.i.g.During this period of increasing temperature and pressure, the mixturewas slowly agitated by means of a wall scraping blade contained withinthe autoclave. At this point the pressure within the autoclave wasgradually reduced to atmospheric over a 30 minute period. During thispressure reduction cycle the temperature was made to level out at 278C., at which point the polymer melt was allowed to equiiibrate for 30minutes.

The resulting molten polymer was melt extruded directly from the bottomof the autoclave through a 14- hole spinneret to yield a whitemulti-filament yarn. Upon being drawn at a draw ratio of 4.85:1 thisyarn exhibited a tenacity of 5.86 grams per denier. The yarn was laterconverted into a fabric suitable for static testing.

Example III A batch of polymer was prepared in the manner identical tothat employed in Example II except that 8.0 weight percent (based on theweight of the unmodified polyamide) of the modifier of Example 11 wasused in lieu of 2.0 weight percent as in Example II.

This finished polymer was then melt spun directly from the bottom of theautoclave through a 14-hole spinneret to yield a white-filament yarn.The yarn was subsequently drawn at a draw ratio of 4.78:1 to yield yarnhaving a tenacity of 6.59 grams per denier. This yarn was laterconverted into a fabric suitable for static testing.

Example IV A batch of polymer was prepared in the manner identical tothat employed in Example II except that 14.0 weight percent (based onthe weight of the uumodified polyamide) of the modifier of Example IIwas used in lieu of 2.0 weight percent as in Example II.

This finished polymer was then melt spun directly from the bottom of theautoclave through a 14-hole spinneret to yield a white-filament yarn.The yarn was subsequently drawn at a draw ratio of 4.67:1 to yield yarnhaving a tenacity of 4.74 grams per denier. This yarn wa later convertedinto a fabric suitable for static testing.

In order to demonstrate the practical usefulness of the modifiedpolyamide, of the present invention, comparative tests of the yarns ofthe above examples were conducted to determine relative decay ordissipation of the electrostatic charge built up on the yarn. As hasbeen stated, the yarns of each of the above examples were converted intoa fabric in the yarn of a knitted tube for convenience in electrostatictesting. The fabric samples of each of the above examples were run atcomparable conditions on a yarn electrostatic measuring instrument todetermine the time required for the decay of one-half of the staticcharge build up on the fabrics. The testing was done and themeasurements were made on a dynamic static tester similar to thatdescribed in detail in vol. 40, American Dyestuff Reporter, pp.164-168(1951).

In brief, the method of testing involves attaching the test fabric to analuminum cylinder which is rotated at approximately 300 revolutions perminute. The fabric on the cylinder of the test instrument is thenelectrostatically charged by allowing it to rub against a second fabricsurface, said second fabric surface being held stationary. After twominutes of rubbing contact, the contact between the two fabric surfacesis broken, and while the fabric on the aluminum cylinder is stillrotating, the time required for the decay of one-half the static chargebuild up on the rotating fabric sample is measured electronically. Alltesting was done at standard conditions, that being 35 percent relativehumidity and 70 F.

The fabric samples of all the above examples were put through a total oftwenty-five standard washings prior to conduction the static tests asabove described with the exception of Example I which was washed fivetimes. The standard washing consists of agitating the fabrics at 140 C.for a period of 20 minutes in a scour solution composed of 0.1 percentTriton X100, which is a nonionic surfactant, and 0.1 percent tetrasodium pyrophosphate, said solution having a liquor-to-fiber ratio of40:1. After five of these washings the fiber samples were dried andconditioned for a period of 24 hours at 35 percent relative humidity and70 F. temperature.

In. these tests, the shorter the time required for the dissipation ofthe half-life of the static charge build up on the fabric, the greaterthe degree of anti-static property. That is to say, the greater theantistatic properties of the fabric the less time required for the decayof half the static charge built up on the fabric.

In the following tests results yarn samples of Example I (filamentsformed from unmodified polyhexamethylene adipamide) are compared withyarn samples of Examples II, III, and IV (filaments formed frompolyhexamethylene adipamide, modified in accordance with thisinvention).

Time (sec.) for static charge Example: decay (half-life), sec. I(control) 6720 II 820 III 38 1V 18 been maintained near the samedesirable levels as those possessed by the unmodified polyamides.

As previously noted, the products obtained in the practice of thisinvention are particularly useful in the manufacture of fibers, fabrics,garments, upholstery and rugs where polyamide filaments having a highstatic electrical charge dissipation are especially desirable. Theproducts obtained in the practice of this invention may also be used toadvantage in the manufacture of films, bristles, coating, and the likewhere the ultimate end use intended will be benefited by the employmentof a polymer having low antistatic characteristics.

As many widely difierent embodiments of this invention may be madewithout departing from the spirit and scope thereof, it is to beunderstood that the invention is not to be limited by the specificembodiments set forth herein but only by claims which follow.

What is claimed is:

1. A fiber-forming synthetic linear polycarbonamide having recurringamide groups as an integral part of the main polymer chain, and whereinsaid groups are sep arated by at least two carbon atoms, containing from0.1 to about 20.0 weight percent, based on the weight of saidpolycarbonamide, of a polyalkoxylated triglyceride of a saturated fattyacid wherein the polyalkoxy portion has a molecular Weight of betweenabout 2,000 and 22,000, and wherein the saturated fatty acid has 10 to30 carbon atoms.

2. A fiber-forming synthetic linear polycarbonamide as defined in claim1 wherein said polyalkoxylated glyceride is polyalkoxylated hydrogenatedcastor oil.

3. A fiber-forming synthetic linear polycarbonamide as defined in claim1 wherein said polyalkoxylated glyceride is polyethoxylated hydrogenatedcastor oil.

4. A fiber-forming synthetic linear polycarbonamide as defined in claim3 wherein said polyethoxylated hydrogenated castor oil is present in anamount of from 1.0 to 15 .0 weight percent, based on the weight of saidpolycarbonamide.

5. The fiber-forming synthetic linear polycarbonamide as set forth inclaim 4 wherein said polycarbonamide is polyhexamethylene adipamide.

6. A textile fiber comprising the polycarbonamide as defined in claim 1.

7. A textile fiber comprising the polycarbonamide as defined in claim 4.

References Cited UNITED STATES PATENTS 3,341,343 9/1967 Beiswanger etal. 26018 X 3,329,557 7/1967 Magat et al. 161-172 3,297,653 1/ 1967Tomiyama et al. 260- 3,052,646 9/1962 Doggett 260-18 X 2,998,295 8/1961Goldann 8115.5 2,252,555 8/1941 Carothers 26078 FOREIGN PATENTS 616,9534/ 1962 Belgium.

635,558 1/1961 Belgium. 1,020,298 2/1966 Great Britain.

820,541 9/1969 Great Britain.

DONALD E. CZAIA, Primary Examiner. C. W. IVY, Assistant Examiner.

